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Know your limits.

Here at ThinkGeek we are definitely fond of the infamous caffeine molecule but we also have another favorite molecule: ethanol. This alcohol is caffeine's older, misbehaving brother. Both molecules can help us get through a rough day, but alcohol warrants the need for a higher level of responsibility and control. Knowing your limits is important and this little device can help you decide whether you should hit the road or call a cab.

The BACtrack Digital Breathalyzer is a compact unit that fits on your keychain or in your bag or purse. Flip the folding mouthpiece, blow, and see your estimated blood alcohol level instantly on the screen in big LED digits. Three optional mouthpieces are also included if you want to test multiple people. Take BACtrack on the town whenever you're out partying. Be sure to check your local laws for the legal limit near you (but seriously, just get a designated driver or call a cab, okay? Timmy needs you in his geek army!).